Carbon fibrils, method for producing same and adhesive compositions containing same

ABSTRACT

This invention concerns a discrete carbon fibril characterized by a substantially constant diameter between about 3.5 and about 70 nanometers, length greater than about 5 times the diameter and less than about 100 times the diameter, an outer region of multiple essentially continuous layers of ordered carbon atoms and a distinct inner core region. The invention further concerns a plurality of such fibrils. 
     The fibrils of this invention may be produced by contacting for an appropriate period of time and at a suitable pressure a suitable metal-containing particle with a suitable gaseous, carbon-containing compound, at a temperature between about 850° C. and 1200° C., or by treating discrete carbon fibrils, characterized by a length greater than about 100 times the diameter. Carbon fibrils may also be continuously produced by continuously contacting for an appropriate period of time at suitable conditions. 
     Another aspect of the invention concerns a composition of matter comprising a carbon fiber or a carbon plate and a plurality of fibrils. 
     Carbon fibrils and compositions of matter comprising carbon fibrils are useful in composites having a matrix of e.g., an organic polymer, an organic polymer or a metal. In specific embodiments, the fibrils or the compositions of matter may be used to reinforce a structural material, to enhance the electrical or thermal conductivity of a material, to increase the surface area of an electrode or capacitor plate, to provide a support for a catalyst, or to shield an object from electromagnetic radiation.

This application is a continuation of application Ser. No. 07/978,634,filed Nov. 19, 1992, abandoned which is a divisional of application Ser.No. 07/593,319, filed Oct. 1, 1990, now U.S. Pat. No. 5,165,909 which isa continuation of application Ser. No. 06/871,676, filed Jun. 6, 1986,abandoned which is a continuation-in-part of application Ser. No.06/678,701, filed Dec. 6, 1984 now U.S. Pat. No. 4,663,230.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of U.S. Ser. No. 678,701,filed Dec. 6, 1984, the contents of which are hereby incorporated byreference into the present application.

This invention relates to the production of graphitic carbon fibrilshaving nigh surface area, high Young's modulus of elasticity and hightensile strength. More specifically, it relates to such fibrils growncatalytically from inexpensive, readily available carbon precursorswithout the need for usual and expensive graphitizing temperatures(approximately 2900° C.).

Fiber-reinforced composite materials are becoming increasingly importantbecause their mechanical properties, notably strength, stiffness andtoughness, are superior to the properties of their separate componentsor of other non-composite materials. Composites made from carbon fibersexcel in strength and stiffness per unit weight, hence they are findingrapid acceptance in aerospace and sporting goods applications. Theirhigh cost, however, inhibits wider use.

Carbon fibers are currently made by controlled pyrolysis of continuousfilaments of precursor organic polymers, notably cellulose orpolyacrylonitrile, under carefully maintained tension, which is neededto insure proper orientation of the anisotropic sheets of carbon atomsin the final filaments. Their high cost is a consequence of the cost ofthe preformed organic fibers, the weight loss in carbonization, the slowrate of carbonization in expensive equipment and the careful handlingnecessary to avoid breaks in the continuous filaments.

There has been intense development of methods of spinning andcarbonizing hydrocarbon pitch fiber to reduce precursor filament costand weight loss. So far, the pitch pre-treatment, spinning conditionsand post-treatments needed to insure correct orientation of the sheetsof carbon atoms in the final products have been nearly as expensive asthe previously noted method involving organic polymers. Both methodsrequire use of continuous filaments to achieve high orientation and,thereby, optimum properties. There is a practical lower limit of fiberdiameter, i.e., 6 to 8 micrometers, below which fiber breakage inspinning and post-treatments becomes excessive.

An entirely distinct approach to carbon fiber formation involves thepreparation of carbon filaments through the catalytic decomposition atmetal surfaces of a variety of carbon-containing gases, e.g., CO/H₂,hydrocarbons, and acetone. These filaments are found in a wide varietyof morphologies (e.g., straight, twisted, helical, branched) anddiameters (e.g., ranging from tens of angstroms to tens of microns).Usually, a mixture of filament morphologies is obtained, frequentlyadmixed with other, non-filamentous carbon (cf. Baker and Harris,Chemistry and Physics of Carbon, Vol. 14, 1978) . Frequently, theoriginally formed carbon filaments are coated with poorly organizedthermal carbon. Only relatively straight filaments possessing relativelylarge graphitic domains oriented with their c-axes perpendicular to thefiber axis and possessing little or no thermal carbon overcoat willimpart the properties of high strength and modulus required inreinforcement applications.

Most reports that cite formation of filamentous carbon do not documentthe particular type of filaments formed, so that it is impossible todetermine whether the filaments are suitable for reinforcementapplications. For example, Baker et al., in British Patent 1,499,930(1977), disclose that carbon filaments are formed when an acetylene ordiolefin is decomposed over catalyst particles at 675°-775° C. Nodescription of the structure of these filaments is given, however. InEuropean Patent Application EP 56,004 (1982), Tates and Baker describethe formation of filamentous carbon over FeO_(x) substrates, but againdo not disclose any information concerning the structure of the carbonfilaments formed. Bennett et al., in United Kingdom Atomic EnergyAuthority Report AERE-R7407, describe the formation of filamentouscarbon from catalytic decomposition of acetone, but also fail to giveany indication of the morphology, and hence suitability forreinforcement applications, of the carbon formed.

Several groups of workers have disclosed the formation of straightcarbon filaments through catalytic decomposition of hydrocarbons.Oberlin, Endo, and Koyama have reported that aromatic hydrocarbons suchas benzene are converted to carbon fibers with metal catalyst particlesat temperatures of around 1100° C., Carbon 14:133 (1976). The carbonfilaments contain a well ordered, graphitic core of approximately thediameter of a catalyst particle, surrounded by an overcoat of lessorganized thermal carbon. Final filament diameters are in the range of0.1 to 80 microns. The authors infer that the graphitic core growsrapidly and catalytically, and that thermal carbon subsequently depositson it, but state that the two processes cannot be separated "becausethey are statistically concomitant." Journal of Crystal Growth 32:355(1976). The native fibers, coated with thermal carbon, possess lowstrength and stiffness, and are not useful as a reinforcing filler incomposites. An additional high temperature treatment at 2500°-3000° C.is necessary to convert the entire filament to highly ordered graphiticcarbon. While this procedure may be an improvement on the difficult andcostly pyrolysis of preformed organic fibers under tension, it suffersfrom the drawback that a two step process of fiber growth and hightemperature graphitization is required. In addition, the authors statenothing regarding deliberate catalyst preparation, and catalystparticles appear to be adventitious. In more recent work, preparation ofcatalytic particles is explored, but the two processes of catalytic coregrowth and thermal carbon deposition are again not separated, ExtendedAbstracts, 16th Biennial Conference on Carbon: 523 (1983 ).

Tibbetts has described the formation of straight carbon fibers throughpyrolysis of natural gas in type 304 stainless steel tubing attemperatures of 950°-1075° C., Appl. Phys. Lett. 42(8):666 (1983). Thefibers are reported to grow in two stages similar to those seen byKoyama and Endo, where the fibers first lengthen catalytically and thenthicken by pyrolytic deposition of carbon. Tibbetts states that thesestages are "overlapping", and he is unable to grow filaments free ofpyrolytically deposited carbon. In addition, Tibbetts's approach iscommercially impractical for at least two reasons. First, initiation offiber growth occurs only after slow carbonization of the steel tube(typically about ten hours), leading to a low overall rate of fiberproduction. Second, the reaction tube is consumed in the fiber formingprocess, making commercial scale-up difficult and expensive.

It has now unexpectedly been found that it is possible to catalyticallyconvert hydrocarbon precursors to carbon filaments substantially free ofpyrolytically deposited thermal carbon, and thereby to avoid thethickening stage reported in the prior art as "overlapping" and"concomitant" with the filament lengthening stage. This ability allowsthe direct formation of high strength fibrils useful in thereinforcement of matrices, in the preparation of electrode materials ofvery nigh surface area, and in the shielding of objects fromelectromagnetic radiation.

SUMMARY OF THE INVENTION

This invention concerns an essentially cylindrical discrete carbonfibril characterized by a substantially constant diameter between about3.5 and about 70 nanometers, e.g. between about 7 and 25 nanometers,length greater than about 5 times the diameter and less than about 100times the diameter, an outer region of multiple essentially continuouslayers of ordered carbon atoms and a distinct inner core region, each ofthe layers and the core being disposed substantially concentricallyabout the cylindrical axis of the fibril. Preferably the entire fibrilis substantially free of thermal carbon overcoat.

The inner core of the fibril may be hollow or may contain carbon atomswhich are less ordered than the ordered carbon atoms of the outerregion, which are graphitic in nature.

The fibril of this invention may be produced by treating an essentiallycylindrical discrete carbon fibril, characterized by a substantiallyconstant diameter between about 3.5 and about 70 nanometers, lengthgreater than about 10² times the diameter, an outer region of multipleessentially continuous layers of ordered carbon atoms and a distinctinner core region, each of the layers and the core being disposedsubstantially concentrically about the cylindrical axis of the fibril,so as to produce the carbon fibril.

The fibril of this invention may also be produced by contacting for anappropriate period of time and at a suitable pressure a suitablemetal-containing particle with a suitable gaseous, carbon-containingcompound, at a temperature between about 850° C. and about 1200° C., theratio on a dry weight basis of carbon-containing compound tometal-containing particle being at least about 100:1.

A carbon fibril may al so be continuously produced by continuouslycontacting for an appropriate period of time at a suitable pressuresuitable metal-containing particles with a suitable gaseous,carbon-containing compound, at a temperature between about 850° C. andabout 1200° C., and recovering the fibrils so produced. The fibrilsproduced by this method may be recovered in association with themetal-containing particles or, alternatively, separated from themetal-containing particles and recovered. The continuous contacting maybe effected by continuously introducing the gaseous, carbon-containingcompound into a reaction zone containing the metal-containing particlesand continuously withdrawing the gaseous carbon-containing compound fromthe reaction zone, or by continuously introducing the metal-containingparticles into a reaction zone containing a defined volume of thegaseous, carbon-containing compound and continuously withdrawing themetal containing particles from the reaction zone, or by continuouslyintroducing both the metal-containing particles and the gaseous,carbon-containing compound into a reaction zone and continuouslywithdrawing both from the reaction zone.

In the above-mentioned method for continuously producing carbon fibrils,the withdrawn gaseous, carbon-containing compound or the withdrawnmetal-containing particles may be treated so as to remove anyundesirable material, i.e. impurities or reaction by-products, and thenreintroduced into the reaction zone.

It is further contemplated that a portion of the fibrils in associationwith the metal-containing particles may be continuously recovered,dispersed with additional metal-containing particles, and continuouslyreintroduced into contact with the gaseous carbon-containing compound.

The contacting of the metal-containing particle with thecarbon-containing compound may be carried out in the presence of acompound, e.g. CO₂, H₂ or H₂ O, capable of reaction with carbon toproduce gaseous products.

Suitable carbon-containing compounds include hydrocarbons, includingaromatic hydrocarbons, e.g. benzene, toluene, xylene, cumene,ethylbenzene, naphthalene, phenanthrene, anthracene or mixtures thereof;non-aromatic hydrocarbons, e.g., methane, ethane, propane, ethylene,propylene or acetylene or mixtures thereof; and oxygen-containinghydrocarbons, e.g. formaldehyde, acetaldehyde, acetone, methanol, orethanol or mixtures thereof; and include carbon monoxide.

The suitable metal-containing particle may be a cobalt-, nickel-, oriron-containing particle, including a particle derived from a metal saltthat is thermally decomposable at a temperature below about 1200° C.,having a diameter between about 3.5 and about 70 nanometers.

Such particles may be supported on a chemically compatible, refractorysupport, e.g., a support of alumina; carbon, including carbon fibers,carbon fibrils, or carbon plates; or a silicate, including an aluminumsilicate.

The suitable metal-containing particle may be encapsulated in carbon ora carbon-containing compound of e.g., a carbide or an organic polymer,including polystyrene and starch.

In one embodiment, the surface of the metal-containing particle isindependently heated, e.g. by electromagnetic radiation, to atemperature between about 850° C. and about 1800° C., the temperature ofthe particle being higher than the temperature of the gaseous,carbon-containing compound.

In a specific embodiment, the metal-containing particle is contactedwith the carbon-containing compound for a period of time from about 10seconds to about 30 minutes at a pressure of from about one-tenthatmosphere to about ten atmospheres. In this embodiment, themetal-containing particle is an iron-containing particle, the gaseouscarbon-containing compound is carbon monoxide and the reactiontemperature is between 900° C. and 1150° C. The contacting may becarried out in the presence of gaseous hydrogen. Additionally, theiron-containing particle may be a particle derived from iron oxalate andmay be supported on a chemically compatible, refractory support of e.g.,carbon.

This invention also concerns a method for producing a substantiallyuniform plurality of essentially cylindrical, discrete carbon fibrilswhich comprises contacting for an appropriate period of time and at asuitable pressure, suitable metal-containing particles with a suitablegaseous, carbon-containing compound, at a temperature between about 850°C. and about 1200° C. Preferably, each of the fibrils so produced has adiameter substantially equal to the diameter of each other fibril. Inone embodiment the metal-containing particles are pre-formed.

The fibrils are useful in composites having a matrix of e.g., an organicpolymer, an inorganic polymer, a metal, an adhesive, or a ceramicmaterial. The fibrils may be dispersed in the matrix, oriented into towsof fibrils which are dispersed in the matrix, or entangled together toform a fibril mat which is disposed in the matrix.

Another aspect of this invention concerns a "furry" fiber, a "furry"plate, or a branched fibril which comprises a carbon fiber, a carbonplate, or a carbon fibril, respectively, and a plurality of carbonfibrils adhering to the outer surface of the fiber, plate, or fibril,respectively. A method for producing furry fibers, furry plates, orbranched fibrils comprises dispersing suitable metal-containingparticles on the outer surface of a carbon fiber, plate, or fibril,respectively, and contacting with a suitable gaseous, carbon-containingcompound for an appropriate period of time and at a suitable pressure.Composites comprising a matrix and furry fibers, furry plates, orbranched fibrils may be produced by e.g., dispersion or impregnation.

Carbon fibrils (including tows of fibrils), fibril mats, furry fibers,furry plates or branched fibrils may be used to reinforce a structuralmaterial, to enhance the electrical or thermal conductivity of amaterial, to increase the surface area of an electrode or anelectrolytic capacitor plate, to provide a support for a catalyst, or toshield an object from electromagnetic radiation.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. A dispersion of catalyst particles comprised of Fe₃ O₄.

FIG. 2. A dispersion of catalyst particles comprised of Fe₃ O₄.

FIG. 3. Catalyst particles encapsulated in 50-150 angstrom carbonsheaths.

FIG. 4. Numerous 100-450 angstrom diameter fibrils, together withcatalyst support and reaction debris.

FIG. 5. A fibril with a diameter of approximately 250 angstroms,together with catalyst support and reaction debris.

FIG. 6. Schematic Diagram of the Continuous Production of CarbonFibrils.

DETAILED DESCRIPTION OF THE INVENTION

An essentially cylindrical carbon fibril may be produced in accordancewith this invention, said fibril being characterized by a substantiallyconstant diameter between 3.5 and about 70 nanometers, a length greaterthan about 5 times the diameter and less than about 100 times thediameter, an outer region of multiple layers of ordered carbon atoms anda distinct inner core region, each of the layers and the core beingdisposed concentrically about the cylindrical axis of the fibril.Preferably the entire fibril is substantially free of thermal carbonovercoat. The term "cylindrical" is used herein in the broad geometricalsense, i.e., the surface traced by a straight line moving parallel to afixed straight line and intersecting a curve. A circle or an ellipse arebut two of the many possible curves of the cylinder.

The inner core region of the fibril may be hollow, or may comprisecarbon atoms which are less ordered than the ordered carbon atoms of theouter region. "Ordered carbon atoms," as the phrase is used herein meansgraphitic domains having their c-axes substantially perpendicular to thecylindrical axis of the fibril.

In one embodiment, the length of the fibril is greater than about 20times the diameter of the fibril. In another embodiment, the fibrildiameter is between about 7 and about 25 nanometers. In anotherembodiment the inner core region has a diameter greater than about 2nanometers.

A method for producing a carbon fibril according to this inventioncomprises treating a second essentially cylindrical discrete carbonfibril characterized by a substantially constant diameter between about3.5 and about 70 nanometers, length greater than about 10² times thediameter, an outer region of multiple essentially continuous layers ofordered carbon atoms and a distinct inner core region, each of thelayers and the core being disposed substantially concentrically aboutthe cylindrical axis of the fibril.

It is contemplated that various treating means are suitable forproducing the carbon fibril. In one embodiment, treating comprisesfragmenting the second carbon fibril by mechanical means, e.g.,grinding, milling. In another embodiment, treating comprises alteringthe second carbon fibril with shear forces that are produced in a fluidmedium. More specifically, the second carbon fibril is contained in aliquid or semi-liquid medium, e.g., a monomer or a matrix. The medium issubjected to processing or handling operations, e.g., extrusion,injection, or molding, so as to produce shear forces sufficient to alterthe second fibril into a fibril in accordance with this invention.

Another method for producing an essentially cylindrical, discrete carbonfibril according to this invention comprises contacting for anappropriate period of time and at a suitable pressure a catalyst, i.e.,a suitable discrete metal-containing particle, with a suitableprecursor, i.e., a suitable gaseous, carbon-containing compound, at atemperature between about 850° C. and about 1200° C. The ratio on a dryweight basis of carbon-containing compound (precursor) tometal-containing particle (catalyst) is suitably at least about 100:1.

A method for continuously producing carbon fibrils comprisescontinuously contacting for an appropriate period of time and at asuitable pressure, suitable discrete, metal-containing particles(catalyst), with a suitable gaseous, carbon-containing compound,(precursor), at a temperature between about 850° C. and about 1200° C.,and recovering the fibrils so produced. In one embodiment, the fibrilsmay be recovered in association with the metal-containing particles. Inanother embodiment the fibrils may be separated and recovered from theparticles, e.g., by extraction of the metal particles into 10% aqueoussolution of hydrochloric acid. The continuous contacting in oneembodiment is effected by continuously introducing the precursor into areaction zone containing the catalyst particles and continuouslywithdrawing the precursor from the reaction zone, e.g., a flow towerreactor with a packed bed or fluidized bed of catalyst. In anotherembodiment, contacting is effected by continuously introducing thecatalyst particles into a reaction zone containing the precursor andcontinuously withdrawing the catalyst from the reaction zone. In anotherembodiment, contacting is effected by continuously introducing both thecatalyst particles and the precursor into a reaction zone andcontinuously withdrawing both from the reaction zone, e.g., a continuouscocurrent or countercurrent flow tower.

In the above-mentioned method for continuously producing carbon fibrils,the withdrawn precursor, catalyst, or both may be treated so as toremove any undesirable material, e.g., impurities, inactive catalyst, orby-products formed during fibril production, and then reintroduced intothe reaction zone. In one embodiment where the precursor is carbonmonoxide, the effluent gas, which is predominantly carbon monoxide,carbon dioxide and trace amounts of impurities, may be treated bypurging a portion of the effluent gas and adding a relatively pureamount of carbon monoxide. Alternately, the effluent gas may be treatedby scrubbing with a suitable carbon dioxide-absorbing compound such asmonoethanolamine (MEA). Still another method of treatment comprisesconverting the carbon dioxide present in the effluent gas to carbonmonoxide, e.g., by passing the effluent gas over or through a carbonsource. In an embodiment where the precursor is a gaseous hydrocarbon,treatment of the effluent gas may comprise removing the hydrogenproduced during fibril production. In another embodiment where thewithdrawn catalyst is treated and reintroduced, treatment may compriseseparating the active catalyst from the inactive catalyst by magneticmeans.

In another embodiment of the continuous production of carbon fibrils, aportion of the fibrils in association with the metal-containingparticles may be continuously recovered, treated with additionalmetal-containing particles and the fibrils so treated are continuouslyreintroduced into contact with the gaseous, carbon-containing compound.Treatment may comprise forming a dispersion of catalyst on the fibrilsas exemplified in example 34.

It is contemplated that a variety of carbon-containing compounds aresuitable as precursors when used with an appropriate combination ofreaction parameters, in accordance with this invention. In one presentlypreferred embodiment, the precursor is carbon monoxide. In otherembodiments, suitable precursors include hydrocarbons. A hydrocarbonprecursor may be aromatic, e.g. benzene, toluene, xylene, cumene,ethylbenzene, naphthalene, phenanthrene, anthracene or mixtures thereof.Alternatively, the hydrocarbon may be non-aromatic, e.g. methane,ethane, propane, ethylene, propylene or acetylene or mixtures thereof.In another presently preferred embodiment, the hydrocarbon is methanebased upon its availability, thermal stability and lack of toxicity. Thehydrocarbon may also contain oxygen, e.g. alcohols such as methanol orethanol, ketones such as acetone, and aldehydes such as formaldehyde oracetaldehyde or mixtures thereof.

Important reaction parameters, in addition to the particular precursor,include catalyst composition and pretreatment, catalyst support,precursor temperature, catalyst temperature, reaction pressure,residence time or growth time, and feed composition, including thepresence and concentrations of any diluents (e.g., Ar) or compoundscapable of reaction with carbon to produce gaseous products (e.g., CO₂,H₂, or H₂ O). It is contemplated that the reaction parameters are highlyinterdependent, and that the appropriate combination of the reactionparameters will depend on the specific precursor carbon-containingcompound.

It is further contemplated that a variety of transition metal-containingparticles are suitable as catalysts when used with an appropriatecombination of reaction parameters. In a presently preferred embodiment,the metal-containing particle comprises a particle having a diameterbetween about 3.5 and about 70 nanometers and contains iron, cobalt ornickel, or an alloy or mixture thereof. Suitable particles may also bederived from metal salts that thermally decompose to metallic particlesor metallic oxide particles at temperatures equal to or below fibrilformation temperatures, i.e. below about 1200° C. Such metal saltsinclude carbonates, bicarbonates, nitrates, citrates, and oxalates,e.g., iron oxalate.

In one embodiment, the metal-containing particle is contacted with thecarbon-containing compound in the presence of a compound capable ofreaction with carbon to produce gaseous products. In one suchembodiment, the compound capable of reacting with carbon is CO₂, H₂, orH₂ O.

It is desirable that catalyst particles be of reasonably uniformdiameter and that they be isolated from one another, or at least heldtogether in only weakly bonded aggregates. The particles need not be inan active form before they enter the reactor, so long as they arereadily activated through a suitable pretreatment or under reactionconditions. The choice of a particular series of pretreatment conditionsdepends on the specific catalyst and carbon-containing compound used,and may also depend on other reaction parameters outlined above.Exemplary pretreatment conditions are provided in the Examples whichfollow. The metal-containing particles may be precipitated as metaloxides, hydroxides, carbonates, carboxylates, nitrates, etc., foroptimum physical form. Well-known colloidal techniques for precipitatingand stabilizing uniform, very small particles are applicable. Forexample, the techniques described by Spiro et al. for precipitatinghydrated ferric oxide into easily dispersible uniform spheres a fewnanometers in diameter, are very suitable for catalyst preparation, J.Am. Chem. Soc.88(12):2721-2726(1966); 89(2):5555-5559 and5559-5562(1967). These catalyst particles may be deposited on chemicallycompatible, refractory supports. Such supports must remain solid underreaction conditions, must not poison the catalyst, and must be easilyseparated if necessary from the product fibrils after they are formed.Alumina, carbon, quartz, silicates, and aluminum silicates such asmullite may be suitable support materials. For ease of removal, theirpreferred physical form is thin films or plates which can easily bemoved into and out of the reactor. It is further contemplated thatcarbon fibers or preformed carbon fibrils may be suitable supportmaterial.

It is also contemplated that a higher productivity of carbon fibrils maybe achieved by initiating fibril growth throughout the reactor volume.Method of initiating fibril growth include dispersing finely divided andevenly distributed catalyst particles throughout the reactor volume. Theparticles may be performed or formed by thermolysis of ametal-containing vapor in the reactor itself. For example, ironparticles may be formed from ferrocene vapor.

The reaction temperature must be high enough to cause the catalystparticles to be active for fibril formation, yet low enough to avoidsignificant thermal decomposition of the gaseous carbon-containingcompound with formation of pyrolytic carbon. The precise temperaturelimits will depend on the specific catalyst system and gaseouscarbon-containing compound used. For example, benzene is kineticallythermally stable to about 1000° C., methane to about 950° C., andacetylene to about 500° C. In cases where thermal decomposition of thegaseous carbon-containing compound occurs at a temperature near or belowthat required for an active, fibril-producing catalyst, the catalystparticle may be heated selectively to a temperature greater than that ofthe gaseous carbon-containing compound. Such selective heating may beachieved, for example, by electromagnetic radiation.

The carbon fibril of this invention may be produced at any desirablepressure, and the optimum pressure will be dictated by economicconsiderations. Preferably, the reaction pressure is between one-tenthand ten atmospheres. More preferably, the reaction pressure is aboutatmospheric pressure.

In one embodiment, the fibril is produced by contacting for a period oftime from about 10 seconds to about 30 minutes and at a pressure ofabout one atmosphere, a suitable iron-containing particle with gaseouscarbon monoxide at a temperature of about 1000° C., the ratio on a dryweight basis of carbon monoxide to iron-containing particle beinggreater than about 1000:1. In another embodiment the fibril is producedby contacting for from about one minute to about five minutes and at apressure of about one atmosphere, a suitable iron-containing particlewith benzene (gaseous) in an approximately 9:1 hydrogen: benzene mixtureat a temperature of about 1100° C., the ratio on a dry weight basis ofcarbon-containing compound to iron-containing particle being greaterthan about 1000:1. In a preferred embodiment of this method, theiron-containing particle is supported on a chemically compatible,refractory support, as previously described. Preferably such refractorysupport is alumina.

Fibrils made according to this invention are highly graphitic as grown.The individual graphitic carbon layers are concentrically arrangedaround the long axis of the fiber like the growth rings of a tree, orlike a scroll of hexagonal chicken wire. There is usually a hollow corea few nanometers in diameter, which may be partially or wholly filledwith less organized carbon. Each carbon layer around the core may extendas much as several hundred nanometers. The spacing between adjacentlayers may be determined by high resolution electron microscopy, andshould be only slightly greater than the spacing observed in singlecrystal graphite, i.e., about 0.339 to 0.348 nanometers.

There are no methods for direct measurement of the physical propertiesof such small fibrils. However, the stiffness of composites containingthe fibrils are those expected from the Young's moduli which have beenmeasured on larger, well graphitized carbons.

Another aspect of this invention concerns a method for producing asubstantially uniform plurality of essentially cylindrical, discretecarbon fibrils. The plurality of fibrils is substantially uniform in thesense that the diameter of each fibril is substantially equal to thediameter of each other fibril. Preferably each of the fibrils issubstantially free of thermally deposited carbon. The method forproducing such a plurality involves continuously contacting for anappropriate period of time and at a suitable pressure, suitablemetal-containing particles, with a suitable gaseous carbon-containingcompound as previously discussed, at a temperature between about 850° C.and 1200° C. By this method a substantially uniform plurality offibrils, e.g. each having a diameter substantially equal to the diameterof each other fibril, may be obtained.

Another aspect of this invention concerns a composite which comprisescarbon fibrils as described above, including composites serving asstructural materials. Such a composite may also comprise a matrix ofpyrolytic or non-pyrolytic carbon or an organic polymer such as apolyamide, polyester, polyether, polyimide, polyphenylene, polysulfone,polyurethane or epoxy resin, for example. Preferred embodiments includeelastomers, thermoplastics and thermosets.

In another embodiment, the matrix of the composite is an inorganicpolymer, e.g. a ceramic material or polyroetic inorganic oxide such asglass. Preferred embodiments include plate glass and other molded glass,silicate ceramics, and other refractory ceramics such as aluminum oxide,silicon carbide, silicon nitride and boron nitride.

In still another embodiment the matrix of the composite is a metal.Suitable metals include aluminum, magnesium, lead, copper, tungsten,titanium, niobium, hafnium, vanadium, and alloys and mixtures thereof.

In still another embodiment, the matrix of the composite is an adhesive.

It is contemplated that the carbon fibrils of this invention may bedispersed into the matrix, oriented in the matrix by means of e.g.,electrical fields, appropriate shearing action or combing, embedded inthe matrix by e.g., impregnation, or injected into the matrix, e.g., bymeans of spray guns.

Carbon fibrils may also be produced in-situ in porous matrices such asceramic material. In one embodiment, such in-situ production comprisesdispersing catalyst in the ceramic matrix and catalytically growing thefibrils in the matrix by passing a gaseous, carbon-containing compoundthrough the porous ceramic matrix.

It is further contemplated that a plurality of carbon fibrils may beprepared in such a way so as to form a fibril mat. In one embodiment ofthe method for continuously producing carbon fibrils, a mat may beproduced by collecting or recovering the fibrils on a support plate orfilter. Suitable recovery filters include surface filters, e.g. screens,and depth filters, e.g. a bed of sand or body of liquid, including amonomer or low oligomer of a polymer. In another embodiment, the fibrilsmay be entangled so as to form a mat.

Another aspect of this invention concerns a "furry" fiber, a "furry"plate, or a branched fibril which comprises a carbon fiber, a carbonplate, or a carbon fibril, respectively, and a plurality of carbonfibrils adhering to the outer surface of the fiber, plate, or fibril,respectively. A method for producing furry fibers, furry plates, orbranched fibrils comprises dispersing suitable metal-containingparticles on the outer surface of a carbon fiber, plate, or fibril,respectively, and contacting with a suitable gaseous, carbon-containingcompound for an appropriate period of time and at a suitable pressure.

Another aspect of this invention concerns a composite which comprisesfibril mats, furry fibers, furry plates, or branched fibrils, asdescribed above. It is contemplated that fibril mats, furry fibers,plates, and branched fibrils may be disposed in a matrix of a compositeby the same means described above for carbon fibrils, e.g. dispersion,impregnation, injection, etc.

The carbon fibrils, fibril mats, furry fibers, furry plates and branchedfibrils are useful in various applications. One application is a methodfor reinforcing a structural material by incorporating therein aneffective reinforcing amount of carbon fibrils, furry fibers, furryplates, or branched fibrils. Another application is a method forincreasing the surface area of an electrode or electrolytic capacitorplate by attaching thereto one or more carbon fibrils, mats, furryfibers, furry plates or branched fibrils. Another application is amethod for supporting a catalyst which comprises attaching a catalyst tothe fibril, mat, fiber or plate of this invention. Such catalyst may bean electrochemical catalyst.

Still another application is a method of enhancing the electricalconductivity of a material. According to this method an effectiveelectrical conductivity enhancing amount of carbon fibrils, mats, furryfibers, furry plates or branched fibrils is incorporated in thematerial.

A further use is a method of enhancing the thermal conductivity of amaterial. In this method an effective thermal conductivity enhancingamount of carbon fibrils, mats, furry fibers, furry plates or branchedfibrils is incorporated in the material.

An additional use is a method of shielding an object fromelectromagnetic radiation by incorporating therein an effectiveshielding amount of carbon fibrils, mats, furry fibers, furry plates orbranched fibrils.

This invention is illustrated in the examples which follow. The examplesare set forth to aid in an understanding of the invention but are notintended to, and should not be construed to, limit in any way theinvention as set forth in the claims which follow thereafter.

EXAMPLES

Materials

The following materials used in the examples below may be obtained fromcommercial sources: Benzene (reagent grade), Fe(NO₃)₃.9H₂ O (BakerAnalyzed Crystal), FeSO₄.7H₂ O (Baker Analyzed Granular), KNO₃ (BakerAnalyzed Crystal) and NaHCO₃ (Baker Analyzed Crystal) may all beobtained from J. T. Baker Chemical Company, Phillipsburg, N.J. CO (C. P.Grade), hydrogen (H₂), and argon (Ar) may be obtained from Air Productsand Chemicals, Inc., Allentown, Pa. KOH (c.P. Pellets) may be obtainedfrom Mallinckrodt Inc., Lodi, N.J. Water used in the examples wasdeionized. Vycor® glass tubes may be obtained from Corning Glass Works,Corning, N.Y. Ceramic combustion boats may be obtained from CoorsPorcelain Co., Golden Colo. Iron oxalate crystals (99.999% iron (II)oxalate dihydrate) may be obtained from Aldrich Chemical Company, Inc.,Milwaukee, Wis. Starch solution (Corn Products starch 3005) may beobtained from CPC International Inc., Englewood Cliffs, N.J. Diglycidylether of bisphenol A (DGEBA) (Araldite 6005) may be obtained fromCiba-Geigy Corp., Ardsley, N.Y.

Davison SMR-37-1534 SRA alumina is an α-boehmite with an averagecrystallite size of 15 angstroms, an average agglomerate size of 0.2microns, and an average particle size of 15 microns.

Degussa Aluminum Oxid C is a α-alumina with a surface of 100 m² /g, anaverage particle size of 200 angstroms, and an apparent bulk density of60 g/L.

Cabot Sterling R V-9348 carbon powder is a furnace black with a minimumcarbon content of 99.5%, a surface area of 25 m² /g, an average particlesize of 750 angstroms, and an apparent density of 16 lb/ft³.

Analyses

All electron micrographs were obtained from a Zeiss EM-10 ElectronMicroscope.

Catalyst Preparations

Example 1 Preparation of Catalyst 1

A magnetite dispersion was prepared according to the method of Sugimotoand Matijevic, J. Colloid & Interfacial Sci. 74:227 (1980). Electronmicroscopy reveals the particle size range to be from 175 to 400angstroms, with 260 angstroms being the approximate average (FIGS. 1 and2).

Example 2 Preparation of Catalyst 2

Into a 4 oz wide-mouth glass jar with a magnetic stirring bar was placed10 g Davison SMR-37-1534 SRA alumina powder. To the stirred powder 0.81MFe(NO₃)₃ in H₂ O was added dropwise to the point of incipient wetness.4.1 mL was required.

Example 3 Preparation of Catalyst 3

A portion of the wet powder obtained in Example 2 was heated in the jarwith stirring on a hot plate until dry. The temperature was kept belowthat at which NO_(X) evolved.

Example 4 Preparation of Catalyst 4

A portion of Davison SMR-37-1534 SRA alumina powder was calcined in anair stream at 900° C. for 90 min in a Vycor® tube. In a 4 oz wide-mouthjar with magnetic stirring bar was placed 1.9977 g of the calcined Al₂O₃. While it was being stirred, 0.81M Fe(NO₃)₃ solution in H₂ O wasadded dropwise to incipient wetness. 0.6 mL was required. The wet powderwas dried with stirring on a hot plate.

Example 5 Preparation of Catalyst 5

Into a 4-in cappable serum polymerization tube was weighed 0.44 gDegussa Aluminum Oxid C (fumed Al₂ O₃). The tube was capped and argonsparged, after which 1 mL 0.5M KOH, 1 mL 2.0M KNO₃, and 6 mL prefiltereddeionized water were injected. The mixture was argon sparged 5 min, then2.0 mL 0.101M FeSO₄ was injected. The mixture was sparged with argon 1min. The tube was placed in a 90° C. oil bath and the argon spargecontinued for 5 min. Sparging was discontinued and quiescent digestionbegun. (The oil bath temperature control was faulty, and temperaturerose to 105° C. The bath was cooled back to 90° C.) Total digestion timewas 2 h.

The system on standing separated into a white precipitate and clearsupernate. It was centrifuged, the supernate decanted, the precipitateresuspended in prefiltered, deionized water. This was repeated two moretimes. The pH on the final supernate was approximately 8.5. The waterwas decanted, the precipitate blown semi-dry with argon, and resuspendedin ethanol.

Example 6 Preparation of Catalyst 6

A portion of Davison SMR-37-1534 SRA alumina powder was calcined 2 h inan air stream at 900° C. in a Vycor® tube. One gram of the product wasplaced in a cappable 4-in polymerization tube and enough 1.6M Fe(NO₃)₃solution was added to cover the alumina completely. The tube was cappedand evacuated until bubbling ceased. It was vented and the excess liquidfiltered off through an M glass fritted filter. The moist cake wascalcined in a ceramic boat for 1 h in an air stream at 500° C.

Example 7 Preparation of Catalyst 7

In a centrifuge bottle 6.06 g Fe(NC₃)₃.9H₂ O was dissolved in 50 mLprefiltered deionized H₂ O. To the solution was added 2.52 g NaHCO₃.When foaming ceased, the solution was sparged 5 min with argon. Theproduct Fe₂ O₃ sol was a clear solution.

A portion of Cabot Sterling R V-9348 carbon powder was calcined in aargon stream in a Vycor® boat in a mullite tube at 1100° C. for 1 h. Itwas cooled to room temperature under argon. Into a 4-in polymerizationtube enough carbon was placed to make about 0.25 in layer. The tube wasevacuated and 2 mL Fe₂ O₃ solution was added. When bubbling ceased, thetube was vented and the suspension filtered on a M-glass fritted funnel.The cake was air-dried and heated for 1 h at 500° C. under an argonstream in a Vycor® tube.

Example 8 Preparation of Catalyst 8

In a 4-in polymerization tube a 0.4876 g portion of calcined CabotSterling R V-9348 carbon powder was evacuated and 2.0 mL 0.81M Fe(NO₃)₃solution was added. When bubbling ceased, the tube was vented and thecake air-dried.

Example 9 Preparation of Catalyst 9

A pellet was made by compressing Cabot Sterling R V-9348 powder in astainless die (for making KBR discs for infra-red). 0.12 g of the pelletwas evacuated in a 4-in polymerization tube and 0.05 mL of afreshly-prepared Fe₂ O₃ sol (prepared as in Example 7) was added. Thetube was vented and the solid was air-dried.

Example 10 Preparation of Catalyst 10

In a 4-in polymerization tube, 0.23 g of Davison SMR-37-1534 SRA aluminawhich had been calcined 2 h at 900° C. in air was evacuated and 2.0 mLfreshly prepared Fe₂ O₃ sol (prepared as in Example 7) was added. Thetube was vented and the solid filtered out on an M-glass fritted filter.The cake was air-dried.

Fibril Synthesis Runs

Examples 11-33

Examples 11-33 describe fibril synthesis runs. Table 1 summarizesexperimental conditions and results. Unless otherwise stated, the fibrilprecursor was benzene as an approximately 9:1 hydrogen:benzene mixture,and gas flow rates were 300 mL/min for H₂ and Ar; 300 mL/min CO and 100mL/min H₂ for CO/H₂ ; 300 mL/min Ar or H₂ through benzene at 20° C. forAr/C₆ H₆ or H₂ /C₆ H₆ (approximately 9:1 volume ratio Ar or H₂ /C₆ H₆).Air and hydrogen were always separated by a brief argon purge of thereactor. Experimental protocols were similar in each run, and aredescribed in detail for Examples 11, 15 and 28.

a) Example 11

Catalyst prepared according to the method of Example 1 wasultrasonically dispersed in water and transferred to a ceramic boat. Theboat was placed in the center of a 1" Vycor® tube in an electric furnaceat room temperature. The catalyst was brought from room temperature to500° C. over a 15 minute period under a flow of argon. At thistemperature, the gas mixture was changed to a hydrogen:benzene (9:1)mixture. This composition was fed into the reactor for 60 minutes.

The hydrocarbon flow was terminated and replaced by argon, and thereactor cooled to room temperature. The boat was removed from the tubeand a quantity of carbon was scraped from it. This carbon wasultrasonically dispersed in ethanol and a 10 microliter sample wasexamined by electron microscopy. The micrographs revealed that most ofthe iron particles were encapsulated in 50 to 150 angstrom carbonsheaths (FIG. 3).

b) Example 15

Catalyst prepared as in Example 2 was dispersed in a ceramic boat. Theboat was placed in a 1" Vycor® tube in the same electric furnace as usedin Example 11.

The furnace temperature was raised from room temperature to 500° C. andfor 60 minutes under air. The reactor was briefly purged with argon. Thetemperature was then raised from 500° C. to 900° C. over a 15 minuteperiod under hydrogen and maintained at 900° C. for 60 minutes underthat hydrogen flow.

Gas flow was then switched to benzene-saturated hydrogen for 180 minutesat 900° C. After cooling to room temperature under argon a sample wasprepared according to the procedure of Example 11, and examined byelectron microscopy. Electron micrographs revealed numerous 100-450angstrom diameter fibrils (FIG. 4).

c) Example 28

Catalyst prepared as in Example 3 was dispersed in a ceramic boat. Theboat was placed in a 1" mullite tube in the same electric furnace asused in Example 11.

The furnace temperature was raised from room temperature to 500° C. over15 minutes and maintained at 500° C. for 60 minutes under air. Thereactor was briefly purged with argon. The temperature was then raisedfrom 500° C. to 900° C. over a 20 minute period under hydrogen andmaintained at 900° C. for 60 minutes under that hydrogen flow. Thetemperature was then raised still further to 1100° C. over a 20 minuteperiod maintaining the same hydrogen flow.

Gas flow was then switched to benzene saturated hydrogen for 5 minutesat 1100° C. After cooling to room temperature under argon a sample wasprepared according to the procedure of Example 11, and examined byelectron microscopy. Electron micrographs revealed fibrils ranging indiameter from 30 to 300 angstroms (FIG. 5).

                  TABLE 1                                                         ______________________________________                                        Fibril Synthesis Runs                                                                Growth            Growth Pre-                                          Example                                                                              Temp.    Catalyst Time   treatment                                                                             Fibrils                               No.    (°C.)                                                                           No.      (min)  Conditions                                                                            Yes  No                               ______________________________________                                        11      500     1        60     25-500° in                                                                          N                                                                15 min (Ar)                                   12      750     .sup. 1.sup.1                                                                          420    23-750° in                                                                          N                                                                40 min (Ar)                                   13      800     3        15     22-500° in                                                                          N                                                                15 min (air)                                                                  500° for 60                                                            min (air)                                                                     500-900° in                                                            15 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                                                              900-800° in                                                            11 min (H.sub.2)                              14      900     .sup. 1.sup.2                                                                          180    26-350° in                                                                     Y                                                                     20 min (H.sub.2)                                                              350° for                                                               15 min (H.sub.2)                                                              350-400° in                                                            10 min                                                                        (CO/H.sub.2)                                                                  400° for                                                               210 min                                                                       (CO/H.sub.2)                                                                  400-900° in                                                            26 min (Ar)                                   15      900     2        180    500° for                                                                       Y                                                                     60 min (air)                                                                  500-900° in                                                            15 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                              16      900     4        180    24-900° in                                                                     Y                                                                     35 min (Ar)                                                                   900° for                                                               60 min (H.sub.2)                              17      900     3        15     80-500° in                                                                          N                                                                15 min (air)                                                                  500° for                                                               60 min (air)                                                                  500-900° in                                                            15 min (H.sub.2)                                                              900 for 60                                                                    min (H.sub.2)                                 18      900     3        60     22-500° in                                                                          N                                                                15 min (air)                                                                  500° for                                                               60 min (air)                                                                  500-750° in                                                            10 min (H.sub.2)                                                              750° for                                                               70 min (H.sub.2)                                                              750-500° in                                                            15 min (H.sub.2)                                                              500° for                                                               60 min                                                                        (Ar/C.sub.6 H.sub.6)                                                          500° for                                                               90 min (H.sub.2)                                                              500-900° in                                                            20 min (H.sub.2)                              19      900     9        60     90-900° in                                                                          N                                                                30 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                                                              900° for                                                               25 min (Ar)                                   20      900     1        60     26-900° in                                                                          N                                                                25 min (Ar)                                   21      900     1        5      220-900° in                                                                         N                                                                20 min (Ar)                                   22     1000     1        5      252-1000°                                                                           N                                                                in 30 min                                                                     (Ar)                                          23     1000     1        120    31-1000°                                                                            N                                                                in 85 min                                                                     (H.sub.2 /C.sub.6 H.sub.6)                    24     1100     5        5      24-500° in                                                                          N                                                                15 min (Ar)                                                                   500-900° in                                                            15 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                                                              900-1100°                                                              in 15 min                                                                     (H.sub.2)                                     25     1100     10       1      24-500° in                                                                          N                                                                55 min (air)                                                                  500° for                                                               60 min (air)                                                                  500-1100°                                                              in 30 min                                                                     (H.sub.2)                                                                     100° for                                                               30 min (H.sub.2)                              26     1100     9        1      140-500° in                                                                         N                                                                10 min (Ar)                                                                   500° for                                                               60 min (Ar)                                                                   500-1100°                                                              in 26 min                                                                     (H.sub.2)                                                                     1100° for                                                              60 min (H.sub.2)                              .sup. 27.sup.3                                                                       1100     5        5      25-500° in                                                                          N                                                                20 min (Ar)                                                                   500-900° in                                                            20 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                                                              900-1100°                                                              in 15 min                                                                     (H.sub.2)                                     28     1100     3        5      25-500° in                                                                     Y                                                                     15 min (air)                                                                  500° for                                                               60 min (air)                                                                  500-900° in                                                            20 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                                                              900-1100°                                                              in 20 min                                                                     (H.sub.2)                                     29     1100     3        1      85-500° in                                                                     Y                                                                     10 min (air)                                                                  500° for                                                               60 min (air)                                                                  500-900° in                                                            20 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                                                              900-1100°                                                              in 10 min                                                                     (H.sub.2)                                     30     1100     6        5      42-500° in                                                                     Y                                                                     15 min (Ar)                                                                   500-900° in                                                            15 min (H.sub.2)                                                              900° for                                                               60 min (H.sub.2)                                                              900-1100°                                                              in 15 min                                                                     (H.sub.2)                                     31     1100     3        5      26-500° in                                                                     Y                                                                     20 min (air)                                                                  500° for                                                               60 min (air)                                                                  500-750° in                                                            10 min (H.sub.2)                                                              750° for                                                               60 min (H.sub.2)                                                              750-500° in                                                            10 min (H.sub.2)                                                              500° for                                                               60 min                                                                        (Ar/C.sub.6 H.sub.6)                                                          500° for                                                               90 min (H.sub.2)                                                              500-1100°                                                              in 30 min                                                                     (Ar)                                          32     1150     8        1      98-500° in                                                                          N                                                                20 min (Ar)                                                                   500° for                                                               60 min (Ar)                                                                   500-750° in                                                            10 min (H.sub.2)                                                              750° for                                                               30 min (H.sub.2)                                                              750-1150°                                                              in 20 min                                                                     (Ar)                                                                          1150° for                                                              15 min (Ar)                                   33     1150     7        1      30-1150°                                                                            N                                                                in 45 min                                                                     (H.sub.2)                                                                     1150° for                                                              15 min (H.sub.2)                              ______________________________________                                         Footnotes to Table 1                                                          .sup.1. Catalyst 1 was heated from 27° to 350° in 10 min        under H.sub.2, from 350° to 500° in 30 min under CO/H.sub.2     held at 500° for 240 min under CO/H.sub.2, and cooled to room          temperature prior to use.                                                     .sup.2. Catalyst 1 was supported on a carbon ber.                             .sup.3. Feed was approximately 18:1 H.sub.2 :C.sub.6 H.sub.6.            

Example 34 Dispersion of Catalyst on Fibrils

Carbon fibrils prepared according to Examples 11-33 may be scraped ontoa sintered glass filter funnel and wetted with a freshly prepared 2%solution of starch. While still wet, the fibrils are treated with a0.81M Fe(NO₃)₃ solution. Excess liquid is poured off and the fibrilsdried in air overnight at room temperature.

Example 35 Production of Branched Fibrils

A small quantity of the fibrils prepared in example 34 may be scrapedinto a ceramic boat and placed in a 1" alumina tube in an electricfurnace. Argon is passed through the tube as the temperature isincreased to 1100° C. Carbon monoxide is introduced for 15 minutes. TheCO flow is terminated and replaced by argon while cooling the reactor.

A quantity of carbon may be scraped from the ceramic boat andultrasonically dispersed in ethanol. A sample may be examined byelectron microscopy to observe new carbon fibrils with diameters rangingfrom 50 to 300 angstroms.

Example 36 Continuous Production cf Carbon Fibrils with Recycle ofPrecursor

A stream consisting of recycle and make-up CO may be fed into a flowtower reactor along with catalyst as prepared in example 34. The flowtower is brick lined and approximately 0.30 meter s in diameter and 20meter s in overall height (FIG. 6).

The mixed recycle and make-up CO stream enters the tower at the top andflows down through ceramic strip heaters which bring its temperature to1100° C. The catalyst is fed by a star feeder into the CO stream.

Gas flow through the reaction zone is 0.16 m/sec and the zone isapproximately 10 meters long. The reaction may be terminated by theinjection of cold (100° C.) gas. Product fibrils are collected on aporous ceramic filter and the effluent gas is recompressed to about 1.3atmospheres. A small purge is taken from the effluent gas to balanceunknown impurities formed in the reactor and contained in the feed CO.The stream passes through a KOH Bed (0.5 m in diameter×2 m long) beforethe make-up CO is added. The stream then is divided; 9 g/second beingdiverted through a heat exchanger and the remaining 3 g/second returnsto the reaction tower.

After 3 hours, the system is shut down and cooled and the ceramic filteris removed. The carbon fibrils are obtained matted to the filter. Thefibrils may be scraped from the filter and used to form a composite.

Example 37 Composite Preparation

An epoxy resin system having 100 parts by weight DGEBA, 36 parts byweight DDS curing agent and 0.5 parts by weight BF₃ MEA accelerator maybe used to wet the mat prepared in example 36 and the resulting massdried overnight at room temperature. Ten one-inch squares are cut fromthe dried mat and placed in a heated die. A composite is formed byhot-pressing for 3 hours at 100° C. The composite is removed from thedisc and aired for 24 hours at 120° C. and 4 hours at 175° C.

What is claimed is:
 1. A fibril mat comprising a plurality of carbonfibrils formed by collecting said fibrils to form a mat, wherein each ofsaid fibrils is characterized by a substantially constant diameter,length greater than about 5 times the diameter, an ordered outer regionof catalytically grown, multiple, substantially continuous layers ofordered carbon atoms having an outside diameter between about 3.5 and 70nanometers, and a distinct inner core region, each of the layers and thecore being disposed substantially concentrically about the cylindricalaxis of the fibril, wherein each of said fibrils is substantially freeof pyrolytically deposited thermal carbon and the diameter of saidfibril being equal to the outside diameter of said ordered outer region.2. A method of producing of a fibril mat of claim 1 which comprisespreparing a plurality of carbon fibrils so as to form a fibril mat bycollecting said fibrils on a filter.
 3. A fibril mat according to claim1, wherein said graphitic domains have c-axes substantiallyperpendicular to the cylindrical axis of the fibril.
 4. A furry fibercomprising a carbon fiber and a plurality of carbon fibrils, whereinsaid fibrils adhere to the outer surface of the fiber and said fibrilsare characterized by a substantially constant diameter, length greaterthan about 5 times the diameter and an outside diameter between about3.5 and 70 nanometers.
 5. A furry fiber according to claim 4, whereinsaid fibrils comprise an outer region of ordered carbon atoms, saidordered carbon atoms comprising graphitic domains.
 6. A furry fiberaccording to claim 5, wherein said graphitic domains have c-axessubstantially perpendicular to cylindrical axis of the fibril.
 7. Afurry fiber according to claim 5, wherein said outer region of orderedcarbon atoms comprises multiple, substantially continuous layers ofordered carbon atoms.
 8. A furry fiber according to claim 7, whereineach of the layers and the core being disposed substantiallyconcentrically about the cylindrical axis of the fibril.
 9. A furryfiber according to claim 4, wherein each of said fibrils beingsubstantially free of pyrolytically deposited thermal carbon and thediameter of said fibrils being equal to the outside diameter of saidordered outer region.
 10. A furry fiber according to claim 5, saidfibrils having a distinct inner core region.
 11. A furry fiber accordingto claim 10, wherein said inner core region contains carbon atoms thatare less ordered than the ordered carbon atoms of the outer region. 12.A furry fiber according to claim 10, wherein said inner core region hasa diameter less than about 2 nanometers.
 13. A furry plate comprising acarbon plate and a plurality of carbon fibrils, wherein said fibrilsadhere to the outer surface of the plate and said fibrils arecharacterized by a substantially constant diameter, length greater thanabout 5 times the diameter and an outside diameter between about 3.5 and70 nanometers.
 14. A furry plate according to claim 13, wherein saidfibrils comprise an outer region of ordered carbon atoms, said orderedcarbon atoms comprising graphitic domains.
 15. A furry plate accordingto claim 14, wherein said graphitic domains have c-axes substantiallyperpendicular to cylindrical axis of the fibril.
 16. A furry plateaccording to claim 14, wherein said outer region of ordered carbon atomscomprises multiple, substantially continuous layers of ordered carbonatoms.
 17. A furry plate according to claim 16, wherein each of thelayers and the core being disposed substantially concentrically aboutthe cylindrical axis of the fibril.
 18. A furry plate according to claim13, wherein each of said fibrils being substantially free ofpyrolytically deposited thermal carbon and the diameter of said fibrilsbeing equal to the outside diameter of said ordered outer region.
 19. Afurry plate according to claim 15, said fibrils having a distinct innercore region.
 20. A furry plate according to claim 19, wherein said innercore region is hollow.
 21. A composition of matter which comprises afirst carbon fibril and a plurality of branch fibrils, wherein each ofsaid branch fibrils adhere to the outer surface of the first carbonfibril and said branch fibrils are characterized by a substantiallyconstant diameter, length greater than about 5 times the diameter and anoutside diameter between about 3.5 and 70 nanometers.
 22. A compositionof matter according to claim 21, wherein said branch fibrils comprise anouter region of ordered carbon atoms, said ordered carbon atomscomprising graphitic domains.
 23. A composition of matter according toclaim 22, wherein said graphitic domains have c-axes substantiallyperpendicular to cylindrical axis of the fibrils.
 24. A composition ofmatter according to claim 23, wherein said outer region of orderedcarbon atoms comprises multiple, substantially continuous layers ofordered carbon atoms.
 25. A composition of matter according to claim 24,wherein each of the layers and the core being disposed substantiallyconcentrically about the cylindrical axis of the fibrils.
 26. Acomposition of matter according to claim 21, wherein each of said branchfibrils being substantially free of pyrolytically deposited thermalcarbon and the diameter of said fibrils being equal to the outsidediameter of said ordered outer region.
 27. A composition of matteraccording to claim 23, said fibrils having a distinct inner core region.28. A composition of matter according to claim 27, wherein said innercore region is hollow.